Budapest’s hottest neighbourhoods are nearly 7°C warmer as mayor warns air conditioning is not the answer

Budapest’s increasingly hot summers are exposing a striking temperature divide across the city, with leafy districts measuring almost 7°C cooler than some of the most densely built-up neighbourhoods. Mayor Gergely Karácsony says the answer should be more greenery, shading and passive cooling rather than simply installing more air conditioners.ú

Karácsony opened his Sunday Facebook post with a joke from a City Hall presentation: a slide supposedly showing the hottest surfaces in the universe featured the Sun, a quasar, a steaming iron – and Budapest’s Baross Square in summer. The comparison may be tongue-in-cheek, but the underlying data are not.

Satellite thermal sensors examined Budapest on 32 summer and four winter occasions between 2013 and 2025, measuring surface temperatures at a resolution of 30 metres at around 9:30 in the morning. Rather than air temperature, the measurements show how hot surfaces such as asphalt, roofs, parks and other urban areas become.

According to Karácsony, a positive urban heat island effect was detectable on 24 of the 32 summer days studied, or 75% of the observations. Budapest was between 0.5°C and 2.6°C warmer than its surroundings.

Nearly 7°C separates Budapest’s coolest and hottest districts

The differences inside the capital are considerably larger. The lowest average surface temperatures were recorded in the greener 2nd and 12th districts, while the highest were found in the densely built-up 6th and 7th districts. The difference between the two extremes reached 6.8°C at the same time of day.

Natural and heavily built-up areas also have strikingly different effects. According to the figures cited by the mayor, the Danube cools its immediate surroundings by around 6.6°C, while the area around Budapest Airport is approximately 5°C warmer.

The findings reinforce a familiar urban pattern: trees, vegetation and water help absorb and dissipate heat, while concrete, asphalt and large built surfaces store it.

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Karácsony warns of an air-conditioning ‘vicious circle’

Air conditioning may provide immediate relief indoors, but Karácsony argued that widespread mechanical cooling can make the wider urban problem worse. He cited a US modelling study in which waste heat released by air-conditioning units increased average night-time temperatures by more than 1°C in some locations.

That creates a feedback loop: hotter nights increase demand for cooling, while the air conditioners themselves release more heat outside.

In Hungary, 27% of homes had air conditioning in 2022, according to census data quoted by Karácsony, although he said the real proportion is now likely to be significantly higher.

The differences between Hungarian cities were already substantial at the time. In Szeged, 46% of homes had air conditioning, compared with 31% in Győr and 19% in Miskolc.

Within Budapest, the 13th district had the highest rate, partly because of its newer housing stock. By contrast, the particularly hot 6th and 7th districts have older buildings and fewer air-conditioned homes.

Heatwave pushed electricity demand up 23%

The growing use of cooling systems is also placing pressure on Hungary’s electricity network. Karácsony said daily electricity demand during the heatwave at the end of June was 23% higher than in the days immediately beforehand.

The problem becomes particularly acute at night. Urban buildings and paved surfaces release the heat accumulated during the day, keeping temperatures elevated even after sunset. At the same time, solar panels stop producing electricity while demand for air conditioning remains high.

Karácsony said Budapest’s response to extreme heat should focus on trees, green spaces, shading and passive cooling, rather than simply installing more air conditioners.

He also called for building renovations that combine insulation with measures such as light-coloured or green roofs, which can help prevent homes from overheating during prolonged hot spells.

The mayor thinks that EU funding could support these broader renovation schemes, including Budapest’s Green Panel programme, and argued that climate adaptation should become a central part of future housing policy.

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